Patent Document 1 discloses a valve timing controller for adjusting a valve timing of an engine utilizing a rotational torque of a motor. The valve timing controller includes a driving circuit that receives a control signal generated by a control circuit and supplies a current to the motor to drive the motor based on a target value of a motor rotation speed represented by a frequency of the control signal, and the driving circuit stops the current supply to the motor when the frequency is lower than a threshold.